Dispensers with automatic roll change are well known. In operation, automatic dispensers often require rolls with a divided core that has to break into two sections as the roll is exhausted and fall out of the dispenser, before the roll change take place. Although a large number of alternative prior art solutions are available, their function and reliability may be affected by a number of inherent problems typical for this type of dispenser.
U.S. Pat. No. 3,770,222 shows a dispenser comprising means for supporting a first roll having spindle means extending axially outwardly beyond the ends thereof in a dispensing position from which flexible sheet material may be withdrawn. The supporting means is operable to move the spindle means of the first roll from a first position when the first roll is full to a second position when the first roll is substantially exhausted. Further means is provided for releasably holding a second roll in a reserve position above the dispensing position and consisting of at least one pivotally mounted lever member extending from the dispensing position to the reserve position, said lever member being engageable with the spindle means of the first roll and operative to sense the position thereof, said lever member being further operative to hold the second roll in the reserve position while said first roll spindle means moves from said first position to said second position and to automatically release the second roll from the reserve position when said first roll spindle means has moved to said second position; and means for guiding the second roll from the reserve position to the dispensing position when the lever member releases the second roll.
One problem with this solution is the difficulty of determining when a roll is substantially exhausted. If the roll is removed before it is exhausted, paper is wasted unnecessarily. On the other hand, the roll must be removed before it is completely exhausted. The latter case may lead to a further problem, wherein a roll that becomes exhausted before it has moved to its second position may remain in or near the dispensing position. This would effectively block the second roll from being moved into the dispensing position. A further problem relates to the friction between the roll support in the dispenser and the spindles or adaptors supporting the roll. In order to ensure that the roll is easily removed from the dispensing position the friction forces should be relatively low, but at the same time the friction forces must be sufficient to prevent excessive amounts of paper from being dispensed if the roll is pulled relatively hard.
The basic problem for dispensers of this type in general is that the automatic roll change is dependent on several different things occurring more or less at the same time. A number of factors can influence the function of a dispenser of this type. For instance, friction forces between roll and dispenser, based on roll size and contact surface, must be reduced below a predetermined limit to allow displacement of the roll. The rotating roll is influenced by forces caused by paper pull or gravity and should be moved out of position before a release mechanism is allowed to release a new roll from a resting position. During these operations the paper shall be completely or substantially exhausted. In many cases something goes wrong here and the automatic roll change is interrupted.
The above problems are solved by an improved dispenser with automatic roll change according to the invention. The dispenser solves the problem relating to the timing of the roll change when the roll is substantially exhausted and provides an improved mechanism for releasing the exhausted roll and replacing it with a reserve roll.